Overload circuit breaker



' Nov. 20,1923

F. TOBIEN OVERLOAD CIRCUIT BREAKER Filed June 12, 1922 Patented Nov. 20, 1923.

I y 1,474,694- UNITED STATES PATENT OFFICEQV' FELIX TOBIEN, OF ESSEN, GERMANY, ASSIGNOR TO FRIED. KRUPP .AKTIENGESELL- SCHAFT, OF.ESSENOHTHE-EUHR, GERMANY.

OVERLOAD CIRCUIT BREAKER.

Application filed June 12, 1922. Serial No. 567,677.

To all whom it may concern:

Be it known that I, FELIX Toninn, residing at EssemGermany, a citizen ofthe German Republic, have invented a certain new and useful Improvement in, Overload Circuit Breakers, of which the following is a specification. y r

This invention relates to improvements in overload circuit-breakers of the kind in which the movable contact member is under the influence of a power accumulator, of a main current releasing coil and of a holding .coil acting in the same sense as the main current releasing coil. a

The invention has for its object to provide an overload circuit-breaker of the said kind with means containing an auxiliary switch and allowing a release of the overload. circuit-breaker to take place even in case no overload prevails in the main circuit, with-- out a disturbing arc-formation being produced at the auxiliary switch.

In order to obtain this object, in accordance with the invention the overload circuit breaker possesses a second releasing coil connected in series with an auxiliary switch and likewise acting in the same sense as the main current releasing coil and being further connected to the circuit to be protected in such a manner that it will be able to receive the current necessary for the release when closing the auxiliaryswitch, and that it will becomecurrentless when cutting out the overload circuit-breaker.

The drawing illustrates, as an embodiment of the subject-matter of the invention, a diagram of an overload circuit-breaker designed to protect a main current motor.

A A designate the main lines which are connected to a source of direct current and from which is branched a line B which con-- tains, in series connection, a starter C C the field winding D} and the armature D cl theniain current motor D D as well as the break formed by-two contact members '0 and e, a blowout-magnet coil e and the main current releasing coil e of an over,

load circuit breaker. Themain current releasing coil 6? is wound around a magnet core E which carries" a contact member c designed to bridge the break 6 c. A spring e engaging the contact member c tends to.

hold theoverload circuit 'breakerin its out- 1n p0s1t1on, shown lnrthe drawing, the spring thus form ng a power accumulator which the main current circuit vis broken,

acts oppositely to the main current releasing coil 6 The magnet core E is, besides, encircled by two other coils c and c" (indicated above the magnetcore E for the sake of clearness). lhe coil 6 serves as holding coil and, along with a series resistance F, it

is connected in parallel to the section of, the main current clrcult containing the main current releasing coil e and the break 6 ct The other coil 67 constitutes the second releasing coil of theoverload circuit-breaker and is connected in series with a resistance G and the ZtLlXllltLP-IY SWllJClLII in a line J which is connected in parallel to the section of the main current circuit containing the motor D D and-the starter C C The auxiliary switch H is constructed as a man-I The two 00118 e and c are ual switch.

wound in a sense and have connections such I I as to cause their numbers of ampere-turns to be added tothe number of ampereturns of the main current releasing coil 6 when a current is flowing through said coils e and c The holding coil 6 is made of the thinnest possible wire and-is of a size such as to enable it to hold the opened overload circuit'breaker inany case in its cut-outposi- I conditions oithe-conta'ct device c c are so that, on the overload circuit-breaker moving into open position, the movable member 6 will be moved'awa'y from the, stationary contact c3 only for a distance so sinall that a short are will be maintained between the two contact members 0 and e until the moment However, in the cut out position oi the'overload circuit-breaker, the distance between the contact members (2 and c is large enough to bar the passage through the releasing .coil 6 of a current shoc'kthat might arise by self-induction of the motor 1) D on switching oil the main current.

The'blowout-rnagnet coil-7c forms part of a sparkblowout device designed to extinguish the break sparks produced at the contact members 6 and cfly I,

Afconductor K including a resistance M,

leads from the lever C of the starter C C to the point of the line J at which the auxilary switch H is connected to the releasing coil 6 The releasing coil 6 is thus connected in parallel to the motor D D through the intermediary of the lines J and K. Therefore, when the motor is in operation, a current will permanently flow through the coil. 6 this current being proportional to the counter-electromotive force of the motor D D The resistance M is of such a strength that the current permanently passing through the releasing coil 6 will not sutlice to cause the overload circuit-breaker to enter into operation as long as the current flowing through the mai current releasing coil 6 does not surpass a maximum value determined in advance. Owing to the parallel connection of the second releasing coil 0 with the motor D D this coil will receive a continuously increasing current during the starting of the motor D D so that the sensibility of the overload circuit-breaker with respect to overload will be lowest at the beginning of the starting operation and highest upon finishing the starting operation. I

The operation of the described device is as :tollows:

hen the motor has been started, a current will normally flow through the main current releasing coil 6 which is not so strong to cause the release of the overload circuit-breaker. The holding coil e will at first remain deenergized inasmuch as it is connected, along with the series resistance F, to two points of the line B between which no remarkable potential dilierence exists when the overload circuitbreaker is closed. At the moment the starting lever C touches the starting resistance C and the motor D D starts rotating, the second re leasing coil 0 will receive a current oi gradually increasing strength which, however, owing to the resistance value chosen for the resistance M, even in combination with the effect of the main current releasing coil will not suflice to cause the release of the overload cilcuitbreaker, as long as no overload circuit will occur.

Ii? the overload circuit-breaker should be caused to act without regard to the strength of the current flowing through the main circuit, the auxiliary switch H has to be closed. By doing this, the circuit A, B, l, G, H, 6 (l, 6, c e 6 c, 6 c, B, A will be closed and the current flowing through the releasing coil 5 will be increased so much that the overload circuit-breaker will act and the main circuit be broken at the contact members 6 e, arcs being thereby produced between the contact members 6*, e and the member 6 Upon releasing the overload circuit-breaker, the contact member e fastened to the magnet core E will likewise be separated from the corresponding stationary contact member This, however, will not cause an immediate interruption of the current in the releasin coil 0 but a short arc will be produced and maintained between the separated contact members e and (2 because of the slight distance between the same. This are will, however, be caused. to disappear again very rapidly, since the arcs formed at the contact members e", e of the (werload circuitbreaker and lying in series with the aforesaid are, are being e:-;tinguished by the spark blowout device 6*". Owing to the rapid extinction ot the are at tie contact members 6 c, the wear of these n'iembers is reduced to a minimum. The effect oi the break 6 0" consists in that it allows, indeed, the releasing current to continue for a short time, but that it opposes to the current shock which the counter-elcctromotive force of the self-induction oi the main current circuit (for example when the motor armatin'e l) is at rest) tends to send through the releasing coil 0 in a reverse direction, a himlrance that cannot be overcome. If this current shock would be allowed to enter into action, it would cause the releasing current in the coil )7 to disappear, the coil would be excited in a sense opposite to the former excitation, the action of the holding coil 1" would be neutralized and a repeated cutting-in and out ot the overload circuit-breakor would be caused. The aioreanentioned are between the contact members 0" and (1 will extinguish along with the extinction of the are at the contact members 0 c ot the overload cir-- cuitbreaker.

i-lit'ter the overload circui't-ljireaker E to c has taken its open position, it being held in that position, contrary to the action of the spring 0, by the holding coil 0 tlnrough which a current is now flowing. in this posi ion of the overload circuit-breake f the auxiliary switch ll may an; in be opened. The formation of an are at the auxiliary switch now impossible, since there is no longer any current flowin through the line B J B broken by the an diary contact device c 6" and the break 0 of the overload circuit-breaker.

If it is desired to return the overload circuit-breaker into its cut-in position, shown in the drawing, it only necessary to re turn the starting lever into the position indicated, in which it is no more in touch with the starting resistance Thereby, the circuit A B C C D D F c B A containing the holding coil c, will become currentless, and the movable contact member E 2 will return into the cut-in position under the action of the sp ringc. The plant is now again ready for working and the motor D D can be started anew.

The main advantage of the device forming the subject-matter of the invention cons1sts in that the overload circuit-breaker can be caused to act any time, without entailing the disadvantage that arcs are produced at the auxiliary switch H used for that purpose. This auxiliary switch can therefore be constructed as a press-button switch or as a relay, without it being necessary to make such press-button switch or relay of large dimensions. l

Another advantage of the described device resides in the possibility to utilize the magnet coil 6 which enables the release of the overload circuit-breaker, also for conforming the sensibility of the overload cir cuit-breaker to the changing conditions of working in such a manner that the overload circuit-breaker possesses a relatively low sensibility during the starting operation and that it reaches its full sensibility only with the increasing counter-electromotive force oi. the motor D D The fact that the wire used for the releasing coil 6 is of larger diameter than the wire used for the holding coil 6 offers the advantage that the magnet coil 0 of the spark blowout device, which is dimensioned for a relatively high current strength, is able to extinguish the break are formed at the contact members 6 6", even'if the overload circuit-breaker should be caused to act while the motor is currentless, such as for example upon switching off the startinglever C Without changing the spirit of the invention, the auxiliary contact device might be omitted and the line J coming from the re leasing coil 6 connected to the movable contact member e of the overload circuitbreaker instead of to its stationary contact member Q The line J containing the releasing coil e would then become currentless at the same moment the breaking oi" the main circuit at the contact members 6 and c will have been completed.

Claims: g

The combination with an overloadcir; cuitbreaker for an electric circuit, comprise a movable contact member adapted to be acted upon by a power accumulator, a main currentreleasing coil and a holding coil wound to act in the same sense as the main current releasing coil, of another releasing coil. lik wise wound to act in the same sense as the main current releasing coil, an auxiliary switch connected in series with the second releasing coil, and electric connections between the second releasing coil and the circuit to be protected for allowing the second releasing coil to receive the current necessary for releasing the overload circuit-breaker upon closing the said auxiliary switch, opening the overload circuit-breaker.

2. In an electric system comprising a,

and to become currentless uponstarter for tie motor and an overload circuitbreaker including amovable contact member adapted to be acted upon by a power accumulator, a main current releasing coil and a holding coil, a second releasing coil arranged for co-operation with the movable contact member and wound to act in the same sense as the main current releasing coil, an auxiliary switch connected in series with the second releasing coil, electric connections between the second releasing coil and section of the main current circuit containing the motor and the starter for allowing this releasing coil to receive, in the open position of the auxiliary switch a current continuously increasing in accordance with the increase of the counter-electromotive force of the motor, the branch line containing the second releasing coil having a resistance valve preventing this releasing coil from causing alone the release of the overload circuit-breaker whenthe auxiliary switch is in open position.

3. In an electric system comprising a main current circuit containing a motor, a starter for the motor and an overload circuit-' breaker including two stationary contact members, a movable contact member, a main current releasing coil and a holding coil, 0. second releasing coil wound to act in the same sense as the main current releasing coil and an auxiliary switch connected in series with the second releasing coil, a branch line of the main current circuit containing the second releasing coil the auxiliary switch, a break arranged in the said branch line and adapted to open and close along with the opening and closing of the overload circuit-breaker.

4e In an electric system comprising a main current circuit containing a motor, a starter for the motor and an overload circuitbreaker including a break formed by two 'stationarycontact members and a movable contact member, a main current releasing coil and a holdlng 0011, a second releas ng coil wound to act in the same sense as the main current releasing coil and an auxiliary taining the second releasing coil and the auxiliary switch.

FELIX TOBIEN.

Certificate .of Correction.

It is hereby certified that in Letters Patent No. 1,474,694 granted November 20, 1923, upon the application of Felix Tobien, of Essen, Germany for an improve ment in Overload Circuit Breakers, an error appears in the printed specification requiring correction as follows: Page 3, line 85,clai1n 2, for the Word Valve read value; and that the said Letters Patent should be read With this correction therein that the same may conform to the record 01. the case in the Patent Oflice.

Signed and sealed thi 8th day of January, A. D. 1924.

[SE/AL] 1 KARL FENNING, v 7 Acting Commc'ssz'oner of Patents.

Cer'tificateof Correction; It is hereby certified that in Letters Patent No. 1,474,694, granted November 20,

1923, upon the application of Felix Toloien of Essen, Germany, for an improvement in Overload Circuit Breakers, an error appears in the printed specification requiring correction as follows: Page 3, line 85; claim 2, for the Word valve read value; and that the said Letters Patent should be read With this correction therein that the same may conform to the record of the case in the Patent Ofiice.

Signed and sealed thi 8th day of January, A. D., 1924.

[SEAL] v KARL FENNING, I Acting Comma'ssioner of Patents. 

